Sprag for one-way clutches



May 20, 1952 l. J. GRUENBERG ETAL SPRAG FOR ONE-WAY CLUTCHES Filed Feb. 2. 1948 2 SHEETS-SHEET l O I N o o I m 0 q- I um BI 10 L n I 9 INVENTORS IVOR J. GRUENBERG y L'EOPOLD T.SZADY ATTORNEYS M y 20, 1952 J. GRUENBERG. ET AL 2,597,241

SPRAG FOR ONE-WAY CLUTCHES Filed Feb. 2, 1948 2 SHEETS-SHEET 2 IN VEN TORS IVOR J.GRUENBERG BY LEOPOLD T4 SZAD Y ATTORNEYS FIG.3.

Patented May 29, 1952 SPRAG FOR ONE-WAY CLUTGHES Ivor J. Gruenberg, Pleasant Ridge, and Leopold T. Szady, Detroit, Mich., assignors to Formsprag Company, Ferndale, Mich., a corporation of Michigan Application February 2, 1948, Serial No. 5,774

1 Claim.

The invention relates to one-way clutches of that type in which driving force is transmitted from one member to another through the medium of sprags interposed between parallel surfaces on the respective members. More particularly, the invention relates to one-way rotary clutches having spaced concentric cylindrical surfaces, respectively, on the driving and driven members with a series of sprags interposed therebetween.

It is the primary object of the invention to obtain a construction of sprag which, when used in a clutch, is most efiicient in its operation and which does not require too close tolerance limits in' the manufacture of the cooperating clutch elements with which it is associated.

It is a further object to obtain a construction of universal sprag which is equally applicable to one-way rotary clutches differing from each other in radial dimensions and. the number of sprags used in each.

, With these objects in view the invention consists, first in a construction of sprag having a cammed end surface so fashioned that when used in a clutch the action angle remains substantially constant for a predetermined portion of said cammed surface and progressively increases, in a succeeding portion thereof. The invention, further consists in a construction of sprag having substantially like opposite end cammed surfaces such that when used in a clutch the action angle has slight variance for a predetermined rotation of the sprag about its own axis with a progressively increa ing action angle during further rotation thereof. Still further the invention consists in the more specific construction of the sprag as hereinafter set forth.

In the drawings:

Fig. 1 is an enlarged elevation of our improved construction of sprag showing, respectively, in full and broken lines two positions of rolling contact with concentric race surfaces in each of which positions the action angle remains constant;

Fig. 2 is a similar view showing a third. position in which the action angle is increased; and

Figs. 3, 4 and 5 are similar views showing a comparison between three types of sprags. also designated in Roman numerals I, II and III, of

which III is our improved construction.

As the general construction of one-way rotary clutches to which our invention is applicable is well-known, we have merely illustrated concentric circles A and B representing, respectively, the spaced inner and outer surfaces of the clutch 2 members between which torque is to be transmitted in one direction of rotation of the driving member. C'is one of the sprags interposed between said surfaces having cammed radially inner and outer ends'D and D, a straight side E extending between said ends and a V-shaped opposite side F having a central rounded nose F for hearing against an adjacent sprag. Such construction can be used to substantially fillthe entire annular space between the inner and outer concentric surfaces of the clutch members, and, because of the v-shaped side, clearance is provided for use in clutches of relatively small radial dimensions and with relatively few sprags in the series. Also the fact. that the straight side of one sprag is adjacent to the nose F of another sprag prevents thecatching of one on the other during rocking movement in or out of clutching engagement.

The cam surfaces D and D can roll in contact with the concentric surfaces A and B during clutching andde-clutching action, and the relative dimensions are such that during initial contact there will be a predetermined action angle between the points of bearing a and b on the respective surfaces. In other words, in one direction of rotation of the driving surface, the point of contact of the cam thereon will be in rear of the point of contact of the cam on the driven surface, and the line a-b connecting these points will be at a predetermined angle to a radial line c-d from the center 0 of the clutch passing through the driving point a. This constitutes the action angle. If, however, there are inaccuracies in the manufacture of the clutch so that the space between the circles A and B is larger or smaller, this will change the points of bearing of the cam surfaces upon their respective concentric surfaces. The amount of rotation of each sprag to compensate for such errors depends upon the design of the cam surfaces. It is possible to so design it that there will be no change in action angle with variation in the dimension between the concentric surfaces. This, however. is not desirable for with increase in torque load the action angle will be diminished due to deformation of the clutch members. In other words, the clutch tends to wind up, the driving member advancing faster than the driven member until the limit of distortion is reached, thus reducing the action angle. On the other hand, the cam may be so designed as to compensate for this deformation and to either maintain the action angle constant or to increase it. The latter would be extent of its rolling surface is notas vgeod for transmission of heavy torque.

In view of the conditions just described, we have designed a sprag having'a cammedend surface with a portion of the rollingsurfadethereof maintaining a substantially constant action angle and a further portion of the rolling surfacewhich has a progressively increasing action angle. The constant action angle portion is of sufiicientezctent to compensate for variations in the spacing stant for a portion of the rolling surface. It is only necessary that the increase in action angle should be relatively small in the first portion of the rolling surface and that there should not be too great a change between successive points in the remaining portion of the surface. As shown 'in' Fig. f1, each-cam surfaceisformed by'tangent arcuate curves of different-raclii; Inithe surface D, the portion of the curve between points I and 2 is an are from the center 3 which is midway between the-inner and outer ends of the sprag and is therefore of a radius approximately onebalf' iof-theravefagediameter of the sprag. The :portion of thecamibetween points 2' and l is an archaving'its center at 5, which is below the point 3, so as to have-a correspondingly greater radius. Thecam D issimilar, the portion of the curve between the points 6 and 1 being concentric with of the concentric surfaces, while'th'esucceeding portion will compensate for deformation of the clutch members under'increased torqueload and to at all times maintain a sufficiently large action angle. J'Ihefollowing table shows the variation in action angle for different degrees of rotation of the spragiin three different'designs of cam', the design Irepr'esented in'column III being the desired construction.

Angle of Action Degrees "Rotation of spray;

' Sprag-I Sprag II SpragII-I -Degreea i'Degrees Degrees 13 V Beyond Limit;

"It will be noted that inicolumn I theaction'angle remains constant :at 4" .during' :rotation of. the sprag i from to 20. In :fcolumn II .the action angle progressively increases and in5' ofrotation of the sprag it is :ohanged'from r" to 7 'In columnIIIIthe action angle remains constant'at 4 for 9 of rotation of thesprag andiprdgressively increases'to 10 up to of rotation of the sprag. This is the principle of construction of .our'improvedspragbut it is not essential thatthe figures should be the same as in column III, or that the angle of action should remain absolutely conthe-pointI-B which is laterally offset from the point 3 but is also midway between the ends of the sprag. 'Theportionofithecurve land 9 has'its center in 'a point it), which iszabove the point 8, a distance-equal to'that between the points? and 5. This construction corresponds to thatof column III of the table. However, as above stated theexactspecific form of -a=curve is nonessential and it need-not be formed of -arcuate portions. 7

' What'we claimas our inventionis: I A sprag having cammed surfaces at opposite ends thereof, .rportions of each of said cammed surfaces being arcs having laterally spaced :respective'centers locatedrmidwaybetweensaidcpposite ends and "other portions of said rammed surfaces being arcs of longer :radi-us =respectively tangent to theiaforesaidiarcs.

lvon J. ERUENBERG. QLEOPOLD :SZADY.

REFERENCES CITED The following references are of "record in the fileof this patent:

Number I Name Date 1;5 42,040 DeLavaud June [6,1925 2,023,961 "Leichsenring r Dec.10, 1935 2,l 13,722 Dodge -s Apr. '12, 1938 FOREIGN PATENTS Number Country Date 637,610 France -May4,1928 

